Make sure you talk to someone who knows how to use them. I think most, if not all are diluted in a carrier oil before applying. And keep them away from cats. I was hoping someone with more experience would chime in and give you more info. on using them.
There are 2 brands that are most used, but my stressed, tired brain isn't recalling the names. They aren't cheap either.
Try a search on home made or natural insect repellents and see what comes up. It might be easier than using EOs. REI might have some. Other outdoor stores may have some too. Here's one from REI, but it might be too smelly for a wedding.
www.rei.com/product/828908/repel-lemon-eucalyptus-pump-spray-insect-repellent-4-fl-oz